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Mansard Loft Conversion

Mansard Loft Conversion

The construction of a Mansard Loft Conversion involves elevating the party wall, which is the wall shared with neighboring properties. While the roof retains its flat structure, one of the external walls slants gently inward. These mansard conversions are commonly situated at the back of a residence and, while applicable to various property styles, they enjoy the greatest popularity among terraced houses.

Benefits of a Mansard Loft Conversion:

Generous Space: A mansard loft conversion provides a considerable amount of usable floor space. The sloping roof and vertical walls create an expansive area that can be customized to meet your specific needs.

Architectural Charm: The distinct architectural style of a mansard roof not only enhances your property’s curb appeal but also adds a touch of elegance that stands out in the neighborhood.

Increased Natural Light: Dormer windows integrated into the mansard loft conversion design allow abundant natural light to flood the converted loft, creating a bright and inviting atmosphere.

Versatility: From bedrooms and home offices to entertainment rooms and playrooms, a mansard loft conversion offers versatility in function, accommodating your family’s changing needs.

Property Value: An expertly executed loft conversion can significantly increase the value of your property, making it a wise investment for the future.

Loft Conversion Planning Permissions

At Studio 20 Architects, we are here to take the complexity out of obtaining planning permission from your council for your project.

We have experienced loft conversion architectural designers and planners. They will prepare astute design and architectural planning strategies. You can rest assured that we will help you secure your planning permission with ease. Contact us now to speak with one of our experts in loft conversions about your project.

Frequently Asked Questions About Loft Conversions​


Do I need planning permission for a loft conversion?

Most loft conversions usually qualify as permitted development, meaning you typically don’t need planning permission if you meet certain criteria. Basic conversions with roof windows are usually fine, but double-check. However, you’ll need permission if you exceed specific limits or alter the roof space significantly.

Can I do a loft conversion under permitted development?

When considering a loft conversion, you can benefit from permitted development rights under certain conditions. To fall within these guidelines, your loft conversion must adhere to the following:

Volume Allowance:

*Terraced Houses: You can add up to 40 cubic metres of additional roof space.

*Detached and Semi-Detached Houses: You can add up to 50 cubic metres of extra roof space.

Roof Slope and Extension:

*The extension must not exceed the plane of the existing roof slope facing the main road.

*The highest point of the extension cannot surpass the highest point of the existing roof.

Materials and Appearance:

*The materials used for the conversion should match the current appearance of the house.

Outdoor Features:

*Verandas, balconies, and raised platforms are not allowed.

Side-Facing Windows:

*Side-facing windows must have obscured glazing.

*Any opening must be positioned at least 1.7 meters above the floor.

Roof Extension Placement:

*Roof extensions (except hip to gable ones) should be set back by approximately 20cm from the original eaves.

Outer Wall Overhang:

*The extension’s roof enlargement must not protrude beyond the outer face of the original house’s wall.

It’s important to be aware that not all properties are eligible for permitted development rights. Properties that do not qualify include:

*Flats and maisonettes.

*Properties located in conservation areas.

*Homes classified as listed buildings.

Do I need building regulations for a loft conversion?

​If you’re considering a loft conversion, it’s important to understand the significance of building regulations approval. This approval is a mandatory step when you’re converting your loft or attic into a functional living space.​

​Thesebuilding regulations hold immense importance as they are designed to guarantee the safety and livability of your home. ​

​They encompass a range of crucial aspects, including:​

Structural Integrity: Assessing whether the newly constructed floor possesses adequate structural strength.​

Overall Stability: Ensuring the stability of your entire loft structure, including the roofing.​

Fire Safety: Implementing measures to ensure fire safety and establishing efficient escape routes.​

Staircase and Floor Safety: Designing your stairs and new floor with utmost safety in mind.​

Sound Insulation: Maintaining reasonable sound insulation between the converted space and existing rooms.​

And More: These regulations cover various other vital factors.​

Due to the intricate nature of these requirements, it’s imperative to collaborate with specialized professionals to meet them. Engaging experts like structural engineers will be essential. Your project will undergo a comprehensive assessment to ensure that all building regulations are met, leading to a successful and secure loft conversion


house extension

Get A Free Quote For Your Loft Conversion Project

Whether you already have some ideas about what you want or you would like to find out more about your options, feel free to contact us. We will arrange an initial consultation at a time that is convenient for you.

​During the consultation, our experts will listen to your ideas and give you professional advice. We will also provide you with a free quote for your project. Please give us a call or send us an email to get in touch with us..

Here’s what our clients have to say.

Nadir is not just an architect… he’s an artist. He listens to his clients and designs and builds for their needs, not to his personal tastes as so many architects do. His genuine skill and willingness to design a project to the client’s needs sets him apart! They were extremely responsive, worked collaboratively with us, and delivered very exciting designs. Highly recommend!
Farkas “Gibkey” Gabor
Farkas “Gibkey” Gabor
I worked with Nadir from Studios Architects on an orangery project. He was very personable and helpful throughout the project and was happy to be on site whenever we asked and gave some good advice. Nadir helped make the project feel seamless and dealt with everything in a polite manner and with ease and good knowledge. I highly recommend.
Natalia G
Natalia G
Nadir was extremely approachable and professional. He was very accommodating as he altered our drawing plans several times on our request and got our plans approved by the council . Many thanks
Behrad Elmiyeh
Behrad Elmiyeh
Despite our best intentions we ran into a rookie planning move, where we allowed scope creep to move us away (incrementally at first) from our approved planning design. Nadir was so polite and even worked with us after hours to understand our issue and offer solutions which ultimately saved us from a potentially costly mistake. The team at studio20 and Nadir in particular are high quality and second to none! I would very highly recommend their services!!
Rodney Charles
Rodney Charles
I’ve worked with Studio20 Architects for my office interior. Menekse and Nadir helped us on interior design of my office to understand the process and was very helpful whenever I had questions. I felt that the team was experienced from Interior design process to project management for all the stages. Highly recommended!!!
Yasemin Hatipoğlu
Yasemin Hatipoğlu
Great service. Coordinated well between builders and structural engineer. The whole team (builders, tilers and painters) all did a quality job and were very very neat and considerate.
Tim Orme
Tim Orme
Excellent ideas and follow up. I have been loo Struggling to find an architect that would understand the complicated structure of my house untill I found these guys. They made things look simple.
Rafiq S
Rafiq S
I've used Studio20 service for planning Single storey rear extension for my South Croydon project. Nadir and his team were very helpful and they explained the process and were always at hand whenever I had questions.
rm rm
rm rm
Contacted Studio20 for some Building Reg and structural drawings Nadir was very efficient and polite he conducted the whole process professionally and with very good knowledge Thank you will definitely recommend
Nasim Chaudhry
Nasim Chaudhry

Popular Questions, you may be interested in

If you are looking to newly build,change the use of your land or building, or for a house extension this means you will need planning permission. A Planning Application includes details of your proposal which is then sent to the Local Planning Authority. LPAs will need to check you application and grant it so that you may start works. Quite simply, it is a way that your local council can check that the proposed development is designed with sensitivity to local guidelines and is suited to the relevant site, street, and area. If we did not have this system in place, we could find buildings that have no uniformity in their designs, form or function. This way, the United Kingdom which is rich in heritage can keep your home as part of it’s identity whilst allowing you to make exciting and necessary changes.

Local Planning Authorities are generally the local council borough and these LPAs will have guidelines and links to explain what are within your rights to make changes to your property. They are usually receptive to pre-applications, but since three years ago, most of the London Boroughs have adopted a fee for their pre-application advise. A good thing to know, no matter if you are doing a small single storey rear extension, a loft converson or a large new build – most LPAs take approximately 6 to 8 weeks to make a decision on your project.

Single-Storey Rear Extensions: The good news is, if you live in a terrced or semi-detached house in 2020, Local Planning Authorities have relaxed the rules and allow for extensions to go to 6 meters . If you live in a detahced house, single storey rear extensions can be up to 8 meters in depth. Just be aware that if your property type is a flat, maisonette or in a conservation area, then you will need full planning permission.

Side Extensions: Side extensions fall under permitted developent if they do not extend more than half the width of the original house. You can extend a maximum of 3 meters as long as it is a single storey extension and does not extend pas the front elevation.

Double-Storey Extension: As of October 2019, new rules are being phased in which will allow homeowners to build extensions onto detached homes without requiring planning permission, under the usual rules of permitted development. This will make adding a two-storey extension to your home no more complicated than having a loft conversion. This doesn’t mean that there is no paperwork involved in undertaking a two-storey extension, but it will make obtaining permission for the extension much simpler.

Loft Extensions: Roof extensions/should be set back, as far as reasonably feasible by at least 20cm from the eaves, unless it is a hip or gable roof (measure the 20cm along the plane of the roof). The roof extension should not hang over the wall of the house.To be a Permitted Development any additional roof space created must not exceed these volume allowances: 40m3 on terraced or emi-detached houses, 50m3 on detached houses.

If you believe that your property falls under permitted development, the best way to ensure a positive result is to consult the advice of an Architect to ensure that your extension follows these rules which are applicable to all extensions:

  • Materials should match the existing house
  • No raised platforms, balconies, or terraces
  • Single storey extensions should not be more than 3 meters high
  • Must not be taller than the existing building
  • The extension should not take more than 50% of garden space

Permitted Development Rights are a set of policies which allow homeowners greater freedom to add value to their home whether it’s increasing your property price or simply to add floor space. By acting upon these rights you can extend your property to a certain degree, without the need for Full Planning Permission, which can be a more expensive and time-consuming process, as long as you comply with relevant rules.

This generally applies to the single-storey side or rear extensions, loft conversions, front porches, double storey extensions, outbuildings, solar panels, skylights of dormer windows and new windows or doors. However, even Permitted Development has its restrictions and does not cover double-storey extensions, larger loft conversions, flats or properties in conservation areas. Regardless, even if you meet all the requirements for Permitted Development, you will still need to submit your plans to council which they will need to check, and approve.

For a full planning application, you will need good knowledge of the local guidlines, an appropriate design and a full set of accurate architectural drawings. Many London Architects will do drawings but not offer extensive planning advice and submit your application on your behalf. On the other hand, Planning Counsultants have expert knowledge of regulations and can therefore play a vital role in obtaining permission for projects with complex needs, but where do both options leave you after your application has been granted…or refused? At Extension Architecture we understand that planning and building involves a lot of head-scratching, that’s why we guide you through the whole process, every step of the way. Extension Architecture specialises in design AND planning consulting and do not charge for submission and liaison with the council. We design, submit planning applications, building regulations with our in-house engineer, construct with trusted buiilders and offer creative interiors with our very own kitchen range. Why bother with the hassle if we can do it all for you?

Building Regulation drawings and control are very important because they insure the safety of people in buildings. Building approval means that your building complies with the national set of standards to protect people’s health and safety in and around buildings. Some examples of what building regulations include are structural calculations, fire-safety, insulation, damp-proofing, foundations, heating, ventilation and accessibilty. Once you have received planning permission, building regulation drawings will have to then be submitted and approved before you can start construction. Just remember, cow-boy builders are always risky business and Local authorities have power under the Building Act 1984 to enforce non-compliant building work altered or removed.

Whether you are considering an extension, a plot development or a conversion, we are here to assist you in gaining LPA approval, maximising the potential of your project which in turn increases the value of your home. At Extension Architecture we offer bespoke packages to suit your budget, ensuring you get the perfect solution for you.

We always provide 2D architectural drawings which detail the design in question. In more complex cases, we can provide 3D visualisations to bring your concepts to life and accurately display the proposed works.

A site assessment will be carried out, either in person or remotely, which will gather information on the existing site. After this, initial drawings are produced and options are discussed with our consultants which leads to amended drawings being made until both parties are happy. At this stage, the application is submitted to the local authority.

All you need to do is fill out our online form which provides us with more information about your project, this way we can get back to you with a more accurate quote. If you would prefer to speak to one of our planning consultants directly, you can call us on 0203 409 4215.

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